Process and apparatus for the fractional distillation of oil



W. G. LAIRD Aug. 23, 1932.

PROCESS AND APPARATUS FOR THE FRAGTIDNAL DISTILLATION OF OIL Filed March 14, 1928 2 Sheets-Sheet l 1932- 'w. s. LAIRD 1,873,135

PROCESS AND APPARATUS FOR THE FRACTIONAL DISTILLATION OF OIL Filed March 14, 1928 2 Sheets-Sheet 2 W/LBL/R ammo v 351;, his

1 WILBUR G. LAIRD, or New YORK, N. Y., AssrsNoR T HEAT TREATING new Yon-x, 1\i. Y., A CORPORATION or DELAWARE Patented Aug. 23, 1932 PATENT? OFFICE coMrAivY, OF

PROCESS AND APPARATUSIFOR THE FRAGTIONAL DISTILLATION'OF OIL Application filed March 14,

This invention relates to a process and apparatus for the fractional distillation of oils, particularly to the fractionation of oils which are made up of a mixture of hydrocarbons of different boiling point or of mixtures of hydrocarbons with other organic compounds. Crude petroleum as it comes from the well is the most abundantoil of this class but it is to be understood that the present invention may be applied to the fractionation of any mixture of liquids in which there is a difference in'boiling point, for example, shale oil, coal tar, various crude cuts of petroleum," cracked petroleum such as synthetic crude or pressure benzine and also a-lcohol'mixtures such as those produced from cracked or natural gas.

Many systems have been devised for the fractionation of oil but they have been adopted more for the production of rough cuts rather than forthe purposeof giving uniform products having definite boiling ranges. With growing competition between oil distributors and refiners it has become more importantthat a suitable marketable product be prepared with as little expense as possible in order to meet competition. Furthermore the product must be as goodas that produced by any one else, or it will be dis-carded by the public for the better product. This is particularly true with respect to motor fuels and lubricants.

The aim of the present invention is, therefore, to provide a process and apparatus of a very efiicient character adapted forthe con-' tinuous resolution of oil mixtures into desired products which will require no further distillation before being placed on the market. 7

The invention with further objects and advantages will be best understood from the following detailed description taken in conjunction with the accompanying drawings, in which: i

Fig. 1 is adiagrammatic flow sheet illus-. trating the'process of and apparatus for fractionation;

. Fig. 2 is an enlarged detail view of aportion of one of the towers shown in Fig. 1,

arts bein broken awa to show the inner 1928. Serial no. 261,431.

structure of certain elements of the apparatus; i i

Fig. 3-is a View of the apparatus shown in Fig. 2, looking from the :right.

Referring to Fig. 1 of the drawings the oil to be fractionated is introduced into the first of a series of distilling units through a pipe 2. From this pipe the oil passes through a group of three condenser-heat exchangers 4, from the last of which it leaves by a pipe6. 'The partially preheated oil now passes through a plurality of condenser-heat exchangers 8,

mounted at the'side of a tower 10. I The path of the oil through these exchangers is indicated by the arrowed line 12 connecting with the, pipe 6. The preheated oil leaving the lowermost exchanger 8, on the tower 10,.is delivered beneath a distributor 14 in a still 16. The still 16 ison'e of a battery of similar stills 16, each ofwhich is set in the usual furnace setting 18. These'stills are shown only diagrammatically, but they are of the usual cylindrical drum type.

Each distilling unit, comprising a still 16 andtower 10, are constructed alike; therefore as far as details are concerned, the description will be confined to a single unit.

The vapors produced in the first still 16 pass by 'a vapor pipe 20 directly into the base ofthetower 10 where they pass alternately through liquid condensate on the bubbler trays and in heat exchange with the down- }wardly advancing charging stock in theheat exchange-condensers 8, the path of vapors 24: into the condensers 4 where they pass 7 counter to and in heat exchange with charging stock. The vapor passages in the con-' clensers 4 are connected by outside vapor lines 26 while the vapors and condensate from the last condenser 4 pass by a pipe 28 into a trap 30. Vapors and gas pass from the trap 30 by a pipe 82 and may be led to a final water cooled condenser, not shown.

In the above described operation the condensate produced in the exchangers 8 flows back onto the bubbletray next below in the tower, while the condensate produced in the condensers 4 may be passed on into the trap 30 with the vapors or all or part of it delivered onto the top bubble tray by the liquid sealed run-back pipes 34. The condensate collected in the trap 30 may be passed to storage or all or part of it returned tothe top bubble tray. The condensate which refluxes downward through the tower 1O flows through the vapor pipe 20 into the still 16 where a re-vaporization of its lighter constituents occurs. r

The unvaporized oilin the firststill 16 is withdrawn through a'pipe 36, in which is inserted a pump 38 forwithdrawing the oil and forcing it upward through'the exchangers8'and 4. The path of the oil through. the tower is indicated by an arrowed line 40. As the residueoil leaves the lastexchanger 4 it passes through a boosterr42, which delivers it a pipe44 to the next distilling unit of theseries whereit passes through a circuit the same as the feed circuit described in connectionwith the first unit.

In each of the distilling units, comprising a still 16 and atower 10, the charging stock is passed in heat exchange but out of contact with the vapors. and unvaporized oil in that particular unit. 1 In each unit the charging stock servesto cool the vapors down to a temperature'suitable' for their subsequent condensation, because the charging stock has a temperature sufliciently low to be able to take 1 up heat from the vapors and therefore aid" in holdingback in the tower the materials which boil higher than the desired out. Since the unva porizedoil leaving any particular unit will be at 'a temperature near the boiling temperature of the vapor cut it is evident that the temperature of the charging stock for the lastunit is much higher than thatof-any preceding unit.

The details of. construction ofthis'tower and the various circuits referred to will be understood best from a description of the en larged showing in Figs. 2 and 3; 7 These fig- V ures show'more in detailthe upper part of one of the towers wherein the reference numerals used in Fig. 1 are applied to corre-' sponding parts. I I

In Figures 2 and 3 the feed oil, or residual oil from a previous still and tower, enters the first ofthe condensers 4 by the pipe 2, where it passes around separate banks of tubes containing vapors and residuum. The

oil leaves the first condenser 4 by a pipe 46 by which it is'introduced into the second condenser'4. In a like manner the oil is con: ducted to the last of the condensers 4 from which it leaves by the pipe 6 and is introduced into the uppermost of the condensers V 8 mountedon the side of the column 10. The

oil being preheated is conducted between the condensers 8 by the pipes 12.

leave the towers above each bubble plate by pipes 48 and pass through a bank of tubes 50 in the condensers 8. Vapors remaining uncondensed in any condenser 8 pass back into the tower proper by a pipe 52 so as to enter in Figures 2 and 3 a chamber is formed above each partition 54 andbelow the vapor pipe 52 which will trap any'condensate' formed therein, such condensate is therefore drained 6 onto the next lower bubble plate by a'pipe which dips into the liquid thereon.

.After passing upward through the column the vapors pass by the vapor line 24 into and through the condensers 4 in the same manner in which they pass through the condensers 8. As shown in Fig. the condensers4 are con nected by vapor lines 26. The vapors condensed, in the. condensers '4 through which the vapors first pass, may be passed by liquid sealed and valved pipes 84 onto the upper bubble tray in the column, or conducted for. ward with the remaining uncondensed vapors and discharged by a pipe "28 into the vapor liquid separator 30. From the separator30 the vapors are passed to a final water cooled condenser (not shown), throughthe pipe. 32, while the condensate is passed therefrom onto the uppermost bubble plate of the column by a liquid sealed and valved pipe 60 or to storage by the valved pipe 62.

The residuum passing up through the tower passes througheach exchanger 8 and 4 by means of the tubes 64 and from exchanger to exchanger by the pipes 40, ina circuit parallel with that of the vapors.

The tower 10 is constructed with the con-' densers 4 and 8 supported on its'shell by suitable brackets. These supporting elements are not shown in the drawings in order to' avoid complication. I

Each heat exchanger or condenser 4 or 8 is constructed on the principle of the known surface condenser except that in the present instance the vapors pass through tubes while the cooling liquid passes therearound. Furthermore, two separate banks of tubes are used in each unit, one for vapors and one for hot residuum. I I I In carrying out the process, for example,

for the fractionation of crude petroleum,

where itvis desired to produce a series of desirable marketable products such as gasoline, kerosene, gas oil, fuel and lubricants, the crude petroleum is introduced into the first still orunit and passed in succession through the whole series of stills in'the' manner discussed above. The cut on the vapors leaving any particular tower may be 'taken as "the vapors enter the pipe 32 so that the desired fraction is actually condensedin a finalwatercooled condenser. However,'-where.the fraction desired is sufliciently' high boiling the cut temperature may be takenin advance of .the condensers 4 or betweenany of thesecondensers so that most of the fractionis withdrawn tromithe trap as condensate. In either case the cut temperature may be accurately maintained and controlled by returning an appropriate amount of condensate from any or all of the condensers 4 back onto the upper bubble plate in the tower. In this sense the condensers 4, as well as the condensers 8, act as reflux or dephlegmating condensers.

In order to secure the maximum heat transfer from the vapors and residuum to the feed oil for any or each unit of the series, a gas or I venlent gas such as the usually produced in the process or other gas not containing tree oxygen or other corrosive constituents is suitable. If a liquid is used it should be selected with more caution since one which would condense with or become absorbed in the oil to any appreciable extent would be undesirable. Water would ordinarily be suitable, and in the production of some of the higher boiling distillates a very light hydrocarbon or oil may be used if the final condenser for the distillate is maintained above the condensing temperature of such a liquid, which in turn may be condensed in a subsequent condenser.

By using a gas or liquid and carrying it forward with the feed there is a marked in crease in vapor formation in the feed stream and consequently a greater heat transfer than usual in heat exchangers, because of the large amount of heat used as heat of vaporization in comparison to the sensible heat transferred in any one temperature range. In order to amplify and promote the vaporization of the constituents in thev feed stream each exchanger 4 and 8 is provided with a distributor 68 (F i g. 2) directly connecting with the pipes 2, 46, 6 and 12 as the case may be, and which is mounted below the tubes and 64 so that any gas or vapor present or produced in the feed stream agitates the oil around these tubes. length of the exchanger, only a part being shown in the broken section in Fig. 2. In certain of the units of the series the charging stock will contain sufficient low boiling material to give some vaporization in the con denser-heat exchangers.

An important feature of the present invention is the provision of a complete vapor '5 tractionating and heat exchange tower for This distributor 68 extends the full each individual stillof the series so that it will be unnecessary, as informer practice, to re-distill each cut to obtainthe desired fraction. iMany-attempts have been m'ade to tractionate' crude petroleum but the ire-running while in the vapor state, to give distillates suitable for market.

In Fig.1 ofith'e drawings only four dis tilling .and'refining'units are shownin series,

1butthe useof a greater or smaller number isinithe contemplated scope {oftheinvention .In any case, the residuumileaving'ithelast tower of the series may be passed to storage by the pipeY-O; 1' c Y Having thus described the i'preterred embodiment :of t'he .new'is:

1. ,An apparatus for distillingwandfractionating liquid mixtures which comprises a series "ofstills,:a fractionating tower for each still, ap'lurality of heat exchangers mounted on each tower, means for passing the liquid .to be distilled in series through the heatexchangerson each tower and into the still for .sai dtowen'mean's for passing hot liquid from each still-through the heat exchangers on the towerof said still andjtromithe heat exchangers of-sa'idto-wer through the heat exchangers of the next tower of the series and into-the still therefor, .and zmeans' ineach towerffor fractional-ting the vapors from the still corresponding thereto.

'2. An apparatus for distilling liquid :mixtures which comprises aseries of distilling and fractionating units, said units comprisinga still and a vapor fractionatingtower, means for introducing'the liquid to be distilled into the first still and then int-o the other stills inseries, means for passing the invention what is'claimed as liquid advancingto each still;in"heat exchange but out of contact with the oil being discharged from saidlstill, means forpassing the vapors-evolved in each still upwardly through the tower corresponding thereto,

means for passing the vapors in each tower alternately through bodies of condensate therein and in heat exchange'but-out of contact with the-li p1id advancing to the still corresponding to said tower and means for refluxing the condensate formed inthe tower of each unit into the still of said unit.

.3. An apparatus for distilling liquid mix tures which comprises a series-of distilling units, each unit comprising a still and hubllO bling plate column, a group of high te'mperature and a group of low temperature 'con- I densers associated with each column, means for passing liquid to be distilled through said stills in series, means for conducting vapors from each column through the condensers associated therewith and for conducting vapors from said group of high temperature condensers back into said column, means permitting the passage of condensate from said condensers onto the hub 'ble plates in the columnassociated therewith,

and means for recovering a definite vapor fraction from each tower.

4. In the distillation of liquid mixtures in which the liquid to be: distilled is passed through a series of distilling zones of increasing temperature to produce a series of rough vapor fractions, the improvement which comprises rectifying thevapors fromeach zone bypassing them alternately in heat exchange but out of contact'with liquid advancing to said. zone and through bodies of condensate produced from such vapors, passing the unvaporized liquid from each zone in heat exchange but out of contact with the liquid 'ad-" vancingv to said zone and recovering a refined vapor fraction from the vaporsfrom 7 each zone.

5. The process of simultaneously producing a series of refined distillates from a crude oil containing a plurality of c'omponents of "different boiling point, which comprises passing the crude oil to be distilled through a series of distilling zones of increasing tem;

'perature to vaporize-successive. portions of the oil, passingthe vapors evolved. in each zone through a rectifying tower where the vapors bubble through pools of condensate, effecting a partial condensation of the vapors leaving each pool by bringing them'in heat exchange but out of contact with oil advancing to the zone in which said vapors were formed, agitating the oil during said heat exchange and recovering arefined distillate from each. tower of, the series. 7 v

6. The process of producing a series of fractional condensates from crude petroleum,

which comprises advancing the crude petroleum to be distilled through a series of distilling zones, of increasing temperature to produce a plurality ofvapor fractions,"subjecting each vapor fraction to rectification by passingit alternately through bodiesof condensate and in indirect heat exchange with oil advancing to the zone in which said fraction was produced, passing a vapor through the oil during said heat exchange to agitate the same and cause vaporization of portions of said oil, and recovering from each zone a refined condensate.

7. The process of producing a series of fractional condensates from a petroleum oil, which comprises passing the petroleum oil to be distilled into the first of a series of distilling zones of increasing temperature and the unvaporized oil from each zone into the next succeeding zone of the series to produce a'vapor fraction in each zone, progressively heating and vaporizing portions of the oil advancing to each zone, maintainingthe va pors produced in said progressive heating 

